This invention relates generally to improved carburetion systems for spark ignited, gaseous fueled engines. More particularly, but not by way of limitation, this invention relates to an improved carburetion system for spark ignited gaseous fueled engines wherein the gaseous fuel has a wide range of heating values.
Over the past several years, due to the relative shortage of fuels having high heating values, it has become desirable to develop an engine that will efficiently utilize gaseous fuels having various heating values, as well as having various chemical compositions. Not only is it desirable that the engine efficiently burn such fuels, but it is highly desirable that such an engine be able to handle various mixtures of such gases. Also, the engine must be able to automatically compensate for the various gases during the operation of the engine.
U.S. Pat. No. 2,744,511, which issued May, 1956 to W. M. Kauffmann, et al, illustrates one attempt to provide a spark ignition internal combustion engine that will utilize gaseous fuels such as natural gas, sewer gas, manufactured gas, etc., while this ratio control system described in the '511 patent is capable of handling the various fuels, the patent indicates that such ratios are controlled in response to the temperature of the exhaust in the exhaust manifold. Utilizing the temperature as a measure will, of course, provide a basis for proportioning the air and fuel. However, it is believed that the utilization of an oxygen sensor provides a better indication of the desired air and fuel ratio for the combustion gases.
The gaseous fuel carburetors currently in use were designed for use with natural gas which has a nominal heating value of about 1000 BTU/FT3. Modifications to the carburetors have been made to permit utilization of fuels, such as sewer gas, having heating values in the range of 600 BTU/FT3. Presently, it is desirable to use gaseous fuels, such as those available from landfills, which have heating values as low as 100 BTU/FT3. To further complicate the carburetion problem, the landfill generated gaseous fuels at a single site may vary in heating value by about 200 BTU/FT3.
Accordingly, an object of this invention is to provide an improved carburetion system for spark ignited, gaseous fueled engines wherein fuels of widely varying heating values and chemical compositions can be readily accommodated and efficiently burned.